STRESS-STRAIN RELATIONSHIP
DOE-HDBK-1017/1-93
Properties of Metals
The Shear Modulus of Elasticity is derived from the torsion of a cylindrical test piece.
Its symbol is G.
The Bulk Modulus of Elasticity is the elastic response to hydrostatic pressure and
equilateral tension or the volumetric response to hydrostatic pressure and equilateral
tension. It is also the property of a material that determines the elastic response to the
application of stress.
To determine the load-carrying ability and the amount of deformation before fracture, a sample
of material is commonly tested by a Tensile Test. This test consists of applying a gradually
increasing force of tension at one end of a sample length of the material. The other end is
anchored in a rigid support so that the sample is slowly pulled apart. The testing machine is
equipped with a device to indicate, and possibly record, the magnitude of the force throughout
the test. Simultaneous measurements are made of the increasing length of a selected portion at
the middle of the specimen, called the gage length. The measurements of both load and
elongation are ordinarily discontinued shortly after plastic deformation begins; however, the
maximum load reached is always recorded. Fracture point is the point where the material
fractures due to plastic deformation. After the specimen has been pulled apart and removed from
the machine, the fractured ends are fitted together and measurements are made of the now-
extended gage length and of the average diameter of the minimum cross section. The average
diameter of the minimum cross section is measured only if the specimen used is cylindrical.
The tabulated results at the end of the test consist of the following.
a.
designation of the material under test
b.
original cross section dimensions of the specimen within the gage length
c.
original gage length
d.
a series of frequent readings identifying the load and the corresponding gage
length dimension
e.
final average diameter of the minimum cross section
f.
final gage length
g.
description of the appearance of the fracture surfaces (for example, cup-cone,
wolf's ear, diagonal, start)
MS-02
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